1. Field of the Invention
An aspect of the present invention relates to an organic light emission diode (OLED) display device and a method of fabricating the same, in which an insulating layer of a non-pixel region is removed to prevent a substrate from being bent or deformed due to an annealing process performed at a high temperature during a crystallization process.
2. Description of the Related Art
In general, polycrystalline silicon is applicable to high field effect mobility and a high operating circuit, and can constitute a CMOS circuit, and thus is widely used for a semiconductor layer of a thin film transistor. The thin film transistor using a polycrystalline silicon layer is generally used as an active element of an Active Matrix Liquid Crystal Display (AMLCD), and a switching element and a driving element of an organic light emitting diode (OLED).
A method of fabricating a polycrystalline silicon layer used for a thin film transistor includes a direct-deposition method, a technique using high-temperature heat treatment and a laser heat treatment method. While the laser heat treatment method enables a low temperature process and a high field effect mobility to be implemented, the laser heat treatment requires a high-price laser device and thus research into techniques capable of replacing the conventional techniques is underway.
Currently, methods of crystallizing polycrystalline silicon using metals are being extensively researched since crystallization can be performed at a lower temperature than that of solid phase crystallization (SPC) within a shorter time period. The methods of crystallizing polycrystalline silicon using metals are classified as a metal induced crystallization (MIC) method and a metal induced lateral crystallization (MILC) method. However, the methods using metals may deteriorate device characteristics of a thin film transistor due to metal contamination.
In the meantime, in order to reduce an amount of metals and to form a high-quality polycrystalline silicon layer, a method in which a metal ion concentration is adjusted by an ion implanter, such that a high-quality polycrystalline silicon layer is formed by a high-temperature heat treatment, a rapid heat treatment or irradiation with a laser is developed. Also, another method has been developed in which, in order to planarize a surface of a polycrystalline silicon layer using the MIC method, a viscous organic layer is mixed with a liquefied metal to deposit a thin film using a spin coating method, and then an annealing process is performed to crystallize. However, in such crystallization methods, problems in terms of large-scale and uniform grains that are the most important issue of the polycrystalline silicon layer are exhibited.
In order to overcome such problems, a method of fabricating a polycrystalline silicon layer through a crystallization method using a capping layer (Korean Patent Publication No. 2003-0060403) has been developed. The method is a super grained silicon (SGS) method in which a polycrystalline silicon layer is formed on a substrate, a capping layer is formed thereon, a metal catalyst layer is deposited on the capping layer, and the metal catalyst is diffused to the polycrystalline silicon layer through the capping layer by means of an annealing process or laser to form a seed, so that a polycrystalline silicon layer is obtained. In the crystallization method, since the metal catalysts are diffused through the capping layer, unnecessary metal contamination can be prevented.
However, forming a polycrystalline silicon layer using the MIC method, the MILC method, or the SGS method requires an annealing process performed at a high temperature, and this may cause an insulating layer formed of the same size as a substrate to shrink, and the substrate may be bent. Furthermore, the shrinking of the insulating layer may cause a device to fail.